This invention relates to a method and apparatus for the chemical analysis of matter. In one aspect, it relates to an injection system for a gas chromatograph or other analytical instrument. In another aspect, it relates to a method of analyzing geological samples to evaluate the petroleum-generating potential of the sample.
In the field of geochemical research and petroleum exploration, an area of growing interest is the analysis of geological samples to determine the remaining petroleum-generating potential of the rock sample. Work in this field has been directed to methods for removing hydrocarbons from geological samples and analyzing the hydrocarbons, to apparatus for laboratory and field analysis of geological samples, and to the development of theoretical and practical models for predicting petroleum-exploration-related characteristics from the raw data obtained. A method known in the art for such analyses involves the thermal extraction of volatile hydrocarbons from a kerogen (insoluble organic portion of sedimentary rocks) or rock sample under carefully controlled temperature conditions and the analysis of the hydrocarbons extracted. In this method, a geological sample is heated to about 300.degree. C. at a constant rate of temperature increase. A gas detecting instrument records signals representative of the quantity of both volatile hydrocarbons and other gases thermally extracted from the sample. The sample is further heated to a higher temperature at a constant rate of temperature increase. A gas detecting instrument records signals representative of the quantity of hydrocarbons and inorganic gases formed by pyrolysis over some predetermined temperature range. The quantities of hydrocarbons formed can be expressed in units of milligrams hydrocarbon per gram sample. One such thermal method involves the controlled heating of a geological sample and the determination of the amounts of hydrocarbons and non-hydrocarbons generated over at least two predetermined temperature ranges. Products thus obtained are reported in units of milligrams of product per gram of rock. These quantities are in turn used to obtain thermal parameters which are used to "type" rock samples according to an established system for categorizing samples in terms of their geological maturity, organic source, and oil-generating potential. The hydrocarbon parameter can be derived mathematically from laboratory analyses which provide the quantity of hydrocarbons generated from a rock, the rock and the total organic carbon in the rock sample.
In performing thermal analyses of geological samples by such methods, it is important to be able to heat the sample to an accurately-determined temperature at a chosen rate of temperature increase. New pyrolysis instruments which are designed for controlled thermal extraction are commercially available but these are generally expensive. Most researchers who are interested in the above analysis have gas chromatography instruments which can perform the analysis of hydrocarbons but which are not capable of heating the sample at a uniform rate as required in the above thermal analysis method. It is thus an object of the invention to provide a universal injection system adapter for a gas chromatograph for thermal analyses.
It is a further object of the invention to provide an adapter for a gas chromatograph or other analytical instrument which provides additional temperature-programming capability to the instrument.